1. Technical Field
The present invention pertains to improvements in methods and apparatus for producing surgical sterile fluid media. In particular, the invention is an improvement of the methods and apparatus disclosed in U.S. Pat. Nos. 4,393,659 (Keyes et al) and 4,934,152 (Templeton) and U.S. patent application Ser. No. 08/213,807 (Faries, et al). The disclosures in those patents are expressly incorporated herein in their entireties by this reference.
2. Discussion of the Prior Art
The Keyes et al patent discloses a surgical slush producing system having a cabinet with a heat transfer basin at its top surface. A refrigeration mechanism in the cabinet takes the form of a closed refrigeration loop including: an evaporator in heat exchange relation to the exterior of the heat transfer basin; a compressor; a condenser; and a refrigeration expansion control, all located within the cabinet. A separate product basin is configured to be removably received in the heat transfer basin. Spacers, in the form of short cylindrical stubs or buttons are arranged in three groups spaced about the heat transfer basin and projecting into the heat transfer basin interior to maintain a prescribed space between the two basins. During use, that space contains a thermal transfer liquid, such as alcohol or glycol, serving as a thermal transfer medium between the two basins. A sterile sheet of material, impervious to the thermal transfer medium, is disposed between the product basin exterior and the liquid thermal transfer medium to preserve the sterile nature of the product basin. Surgically sterile liquid, such as sodium chloride solution, is placed in the product basin and congeals on the side of that basin when the refrigeration unit is activated. A scraping tool is utilized to remove congealed sterile material from the product basin side to thereby form a slush of desired consistency in the product basin.
As noted in the Templeton patent, the above-described system has a number of disadvantages. In particular, the separate product basin must be removed and re-sterilized after each use. Additionally, the glycol or other thermal transfer medium is typically highly flammable or toxic and, in any event, complicates the procedure. The Templeton patent discloses a solution to these problems by constructing an entirely new apparatus whereby the product basin is eliminated in favor of a sterilized drape impervious to the sterile surgical liquid, the drape being made to conform to the basin and directly receive the sterile liquid. Congealed liquid is scraped off the sides of the conformed drape receptacle to form the desired slush.
In addition, Templeton also provides an electrical heater disposed at the bottom of the basin to convert the sterile slush to warmed liquid, or to heat additional sterile liquid added to the basin. Templeton describes the need for such warmed sterile liquid as occurring after a surgical procedure is completed to facilitate raising the body cavity of the surgery patient back to its normal temperature by contact with the warmed liquid. However, there are a number of instances during a surgical procedure when it is desirable to have simultaneous access to both the sterile warmed liquid and the sterile surgical slush, and, on occasion, a supply of near-freezing liquid-state sterile fluid. For example, if the surgical slush is not at the desired consistency (e.g., too thick), the availability of warmed sterile liquid to be added to the slush permits rapid adjustability of the slush consistency. Likewise, maintaining instruments at or near body temperature during surgery is a desirable feature permitted by warmed sterile liquid. Of course, if the warmed sterile liquid is simultaneously available with the surgical slush, there is no need to wait for the slush to melt at the end of the surgical procedure. Finally, the simultaneous and separate provision of slush and warm and near-freezing liquid permits different sterile media to be used as is sometimes necessary for various surgical procedures.